I reported this problem a few days ago, they are still working on optimizing the code, but there's lots of other issues they have to prioritize too I'm sure, PVP crashing due to network problems, which has been wayyyy better since v1.04, and then just complete crashes in general. Anyways it's probably not ATI or nVidia. I have 2 computers identicle other then the video cards, one has a nVidia GTX580 the other has an ATI 5780 (I think I forgot exactly but it doesn't matter here because) they both lag in view mode, bad... I get the stuttering, the 30 seconds of complete freezing, and then it moves again. It appeared more like a cpu/optimization issue to me, but I'm hardware/network guy more, so the devs will have a much better idea then me =) All I know about coding is there isn't a wall thick enough for how many times you bang yer head against it while trying to get things to work properly.
edit: forgot to mention I'm running Intel core i7-920's on those rigs.